The present invention concerns a windscreen wiper device for a motor vehicle with at least one wiper motor, in particular a reversing motor, on which is provided a motor crank which is connected with at least one gearing connected downstream of the wiper motor in order to drive a wiper arm coupled therewith such that it executes an oscillating wiping movement on a windscreen of the motor vehicle, wherein the wiper motor is coupled with a control unit to control the wiping movement, by means of which unit a motor power generated by the wiper motor can be adjusted as a function of a position of the gearing or wiper arm on the windscreen. The invention furthermore concerns a method for controlling the windscreen wiper device.
Such a windscreen wiper device is known for example from document DE 101 44 985 A1. This document discloses a method to control a windscreen wiper device in which the motor power of the wiper motor is controlled as a function of a translation ratio resulting from the position of the gearing, and the motor power and a torque acting on the gearing or the wiper arm are adapted to the power required to carry out the wiping movement of the wiper arm. For this the torque which can be emitted by the wiper motor at any time is determined taking into account the gearing ratios and thus effectively prevents an overload of the wiper motor for example due to snow or ice on the windscreen, as blocking of the windscreen wiper device because of the large masses to be moved can be prevented. The windscreen wiper device reacts particularly sensitively to such masses shortly before reaching the turning positions of the wiper arms in which the wiping direction of the wiper arm reverses. In the turning positions however usually a substantially lower moment is required to drive the wiper arm. In the known wiper system with electronically controlled torque limitation in the prior art therefore, in the wiper arm turning positions the torque is reduced according to need, wherein the demand results substantially from the course of the translation ratio of the wiper linkage or gearing. Because of this control, in the event of blocking a reduced system load occurs which is uniform across the working region.
On acceleration of the wiper arm or motor crank from the turning positions, it must also be ensured that sufficient power can be provided by the wiper motor. The wiper motor must be brought up to higher rotation speed ranges as quickly as possible after reversing.
The power of wiper motors and in particular their starting torques are designed taking into account so-called worst case peripheral conditions, such as for example a drying windscreen, maximum possible wiper arm contact force etc., in order to ensure perfect wiping operation of the windscreen wiper device in this case too. This leads to motors with very high torque, the starting torque of which forms the basis for the dimensioning of the mechanical components of the wiper motor or drive linkage of the windscreen wiper device and the wiper arm. This undeniably leads to individual components having to be dimensioned correspondingly large in order to be able to tolerate the maximum forces, which leads to a higher weight and higher costs.